TWI667353B - Manufacturing method of porous magnesium alloy - Google Patents

Abstract

The invention relates to a manufacturing method of a porous magnesium alloy, which is a mixture of magnesium powder, aluminum powder and urea, and then compacted into a green embryo through a mold, and using a solvent to melt the sacrificial material urea inside the green embryo The porous magnesium alloy is produced by solid phase sintering, and the porous magnesium alloy produced by the invention has the advantages of high pore uniformity, easy control of porosity, simple process, short manufacturing cycle, mass production, and low cost It is an ideal porous magnesium material. It is lightweight, low density, high rigidity, shock absorption, damping, sound absorption, heat dissipation, fire prevention, good energy absorption and electromagnetic shielding. It can be used in a wide range of fields, including: steam Anti-collision materials for locomotives, sound-absorbing materials for roads, fire-resistant materials for buildings, materials for ships and aerospace industries.

Description

Manufacturing method of porous magnesium alloy

The invention relates to a method for manufacturing a porous magnesium alloy, which mixes and compacts a metal powder with a sacrificial material to form a green embryo, and uses a solvent to melt the sacrificial material before sintering a porous magnesium alloy. The process of the present invention has The advantages of easy porosity control, lower cost, simple manufacturing process and short manufacturing cycle.

According to press, lightweight materials have always been the focus of research and development in various countries around the world. Among the porous materials such as polymer materials, glass materials, ceramic materials and metal materials, they have been widely studied and discussed because of their characteristics of effectively reducing density and retaining some raw materials. Among them, the porous metal has a high strength-to-weight ratio, and at the same time has good impact resistance and excellent energy absorption properties, it also has characteristics such as damping, sound absorption, heat dissipation, fire prevention, and electromagnetic shielding, so it has various industrial applications. Good potential.

Secondly, the porous metal material has the characteristics of multiple pores, light weight, small density, high rigidity, shock absorption, damping, sound absorption, heat dissipation, fire prevention, good energy absorption and electromagnetic shielding. It is currently used in the outer plywood of automobiles and beside highways. Of sound-absorbing walls, lightweight structural fillers, heat exchangers, aviation liquid storage equipment, fuel cell electrodes, seismic structural materials, biomedical materials, fire barriers, and military uses, well-known production companies worldwide, Germany Alulight, Alcarbon, Alporas in Japan, Duocel in the United States, Cymat, Alcan in Canada and Hydro in Norway all have their applications.

Among them, when the porous metal is subjected to pressure or impact, the structure will undergo a large amount of deformation, and the stress value is low during the deformation process. Therefore, the porous metal can be made into an energy absorption device, which is placed on the guardrail when the guardrail is subjected to Absorb energy during impact. The porous metal energy absorption device can also be installed between the bumper and the body of the car. When the vehicle collides, it can absorb a large amount of kinetic energy, which not only effectively reduces the damage of the impact to the passengers, but also reduces the damage to the structure of the car body. .

In addition, the porous metal has good sound absorption effect, and can be applied to sound absorption equipment, which can be erected in tunnels, on both sides of highways or under viaducts, etc., and can be used to absorb noise generated by cars, trains, and high-speed rails.

Today's porous metal processes are generally divided into two categories: melting processes and powder processes. The melting process is more suitable for making large-scale workpieces. In small and special-shaped parts, it is very difficult to produce by the melting process, mainly The reason is limited by the size of the mixing equipment and mold during the manufacturing process. Compared with the melting process, the powder process can produce small-sized, special-shaped and porous metal with better pore uniformity, which has attracted high attention. The powder process can be subdivided into the foaming method (TiH ₂ , CaCO _3, etc.) foaming method or the sacrificial material (Carbamide, NaCl, etc.) sintering and dissolution process technology (SDP) ... etc.

The present invention specifically develops a porous magnesium alloy using spherical urea as a sacrificial material and a dissolution and sintering process technology. The porous magnesium alloy produced by the present invention has high pore uniformity, easy to control porosity, simple process, short manufacturing cycle, It can be manufactured in large quantities with low cost.

The present invention relates to a method for manufacturing a porous magnesium alloy. The main purpose of the development of porous metals today is to reduce the density of materials. The most common material is porous aluminum, and magnesium is the lightest structure. Metal materials, but magnesium is prone to corrosion, oxidation and other characteristics at high temperatures, so it is not easy to develop and produce. Therefore, the present invention uses a relatively new sintering dissolution process (SDP, Sintering Dissolution Process) in the metal powder process to produce porous magnesium materials, and sacrifices the choice of materials Urea (Carbamide) with low cost, high solubility and spherical shape.

First, the manufacturing process of the present invention is divided into 1, powder material mixing stage. 2. The stage of making raw embryos. 3 The stage of melting sacrificial materials. 4. Sintering stage. 5. Finished porous magnesium alloy. Among them, in the powder material mixing stage, the ratio of the magnesium powder to the aluminum powder is 9: 1, 19: 1 or other ratio, and the weight percentage of the sacrificial material urea is 40 ~ 60%, and it needs to be on the urea before powder mixing Spray 2vol% ethanol, then pour it into V-type mixer and mix for 1-2 hours.

Secondly, in the stage of making green preforms, the mixed powder needs to be compacted to make it solidify and form. The production of green preforms of the present invention is made by hydraulic press, and the mixed powder is filled into the mold In the mold, the uniaxial pressing is carried out with a pressure of 200-400Mpa, and a holding pressure of 1-2 minutes under equal pressure is given. Finally, the ejected device is used to eject the formed green embryo in the mold, and The green embryo after forming.

Next, the urea, the sacrificial material inside the green embryo, is removed. The urea (Carbamide) is a colorless crystal or powder. Under the action of water, urea is decomposed into ammonia and carbon dioxide. Its chemical reaction formula is CO (NH ₂ ) ₂ + H ₂ O = CO ₂ ↑ + 2NH ₃ ↑, that is, this phenomenon can be used to dissolve and remove the internal sacrificial material urea to make a hole-like structure inside the green embryo, and then put the hydrolyzed green embryo into a heating furnace to heat , And then perform the drying process to remove the moisture inside the green parts. Especially before the drying process, it must be confirmed that most of the urea is dissolved. If it is not completely dissolved, it will cause defects in the drying process.

In the sintering stage, the green embryo part through the drying process is placed in a dry pot and placed in the center of the vacuum furnace, and then evacuated by a vacuum pump to a pressure of less than 3Pa (about 2 × 10) in the furnace ^-2 torr), filled with a protective gas mixture of sulfur hexafluoride (SF6) and carbon dioxide (CO ₂ ) to prevent the oxidation and combustion reaction of porous magnesium materials at high temperature. The rising curve of the sintering temperature of the vacuum furnace is 4 ° C per minute, and the sintering temperature is maintained at 400 ° C to 600 ° C, and the holding time is 2 to 3 hours. The final porous sintered magnesium material will be naturally cooled to room temperature in the furnace .

The key control parameters of the present invention are: the holding time of compaction, the ratio of magnesium powder to aluminum powder, the weight percentage of urea, the time of powder mixing, the temperature of sintering, and the time of sintering all affect the pore size distribution of magnesium alloy and The strength of the magnesium alloy, so the present invention is tested and improved, using the best process technology, the developed porous magnesium alloy can be applied to the anti-collision materials of steam locomotives, highway sound-absorbing partitions, building firewalls, ships, aviation aerospace ... materials in other fields.

〔this invention〕

a‧‧‧Powder material mixing stage

b‧‧‧ Stage of making green embryo

c‧‧‧The stage of melting sacrificial materials

d‧‧‧Sintering stage

e‧‧‧Porous magnesium alloy products

e1‧‧‧Anti-collision material

e2‧‧‧Fireproof material

e3‧‧‧ Sound-absorbing material

1‧‧‧ Raw embryo parts

10‧‧‧Metal powder

11‧‧‧ Urea

12‧‧‧Magnesium powder

13‧‧‧Aluminum powder

2‧‧‧Mixer

3‧‧‧Mould

5‧‧‧Vacuum furnace

51‧‧‧ Dry pot

52‧‧‧Vacuum pump

23‧‧‧ Mixed gas

Figure 1 is a production flow chart of the present invention.

Figure 2 is a schematic diagram of the staged operation of the present invention.

Fig. 3 is a motion diagram of the compaction of the metal powder of the present invention.

Figure 4 is a perspective view of the green embryo of the present invention.

Fig. 5 is a schematic diagram of melting the sacrificial material of the green embryo of the present invention.

Figure 6 is a perspective cross-sectional view of the present invention forming a porous porous green part.

Fig. 7 is a schematic diagram of the sintered porous green embryo part of the present invention.

Figure 8 is a perspective view of the porous magnesium alloy of the present invention.

Fig. 9 is an embodiment diagram of the porous magnesium alloy of the present invention.

Figure 10 is a schematic diagram of the use of the porous magnesium alloy of the present invention.

The present invention relates to a method for manufacturing a porous magnesium alloy. The main purpose of the development of porous metals today is to reduce the density of materials. The most common material is porous aluminum, and magnesium is the lightest structure. Metal materials, but magnesium is prone to corrosion, oxidation and other characteristics at high temperatures, so it is not easy to develop and produce. Therefore, the present invention uses a relatively new sintering dissolution process (SDP, Sintering Dissolution Process) in the powder process to produce porous magnesium materials, at the expense of material selection costs Urea (Carbamide) with low solubility, high solubility and spherical shape.

First of all, please refer to FIG. 1, which is the manufacturing flow chart of the present invention, and its manufacturing procedure is 1, powder material mixing stage a. 2. Stage b of making green embryos. 3. Stage c of melting the sacrificial material. 4. Sintering stage d. 5. Finished porous magnesium alloy e. Among them, in the powder material mixing stage a, it first sprays 2 vol% ethanol on the urea 11, which can increase the binding degree and uniformity of the urea 11 and the powder, and then the ratio is 9: 1, 19: 1 or other ratios The magnesium powder 12 is mixed with the aluminum powder 13.

Secondly, please continue to refer to the second figure, which is a schematic diagram of the staged operation of the present invention. The magnesium powder 12, aluminum powder 13 and urea 11 are poured into the V-type mixer 2 for mixing for 1-2 hours. The time will affect the uniformity of the pores of the porous magnesium material and the degree of oxidation of the powder surface, which will affect its mechanical properties; too short mixing time will cause the urea 11 particles to be too concentrated, and the appearance of the porous magnesium material will be flawed after dissolution If the time is too long, the surface of the powder will be excessively oxidized, resulting in a decrease in mechanical properties and an increase in the cycle time of the process. Therefore, the present invention uses mixing for 1 hour after testing to achieve uniform mixing.

Then, please continue to refer to Figure 1 and cooperate with Figure 3, as shown in Figure 3, the stage of making green embryo parts is to compact the metal powder 10 (Compaction) to make the metal powder 10 from loose to a solid body. 1 (as shown in Figure 4) is also the main key to the formation of porous magnesium materials. Too little pressure will cause the green embryo 1 to have insufficient density and insufficient mechanical bonding force. The green embryo 1 will produce cracks when subjected to a slight collision. It breaks or even turns into powder before molding, and the green embryo 1 of the present invention is made by a hydraulic press, the mixed metal powder 10 is filled into the molding die 3, and then the pressure is 200-400Mpa. Press the shaft and give it a pressure of 1 minute under the same pressure, and finally eject the green embryo 1 in the mold 3 with the ejector.

Next, please continue to refer to the figure 5 to remove the melting sacrificial material stage c of the green embryo 1, the urea 11 is a colorless crystal or powder (not shown in the figure), and the urea 11 can be decomposed under the action of water The chemical reaction formula of ammonia and carbon dioxide is CO (NH ₂ ) ₂ + H ₂ O = CO ₂ ↑ + ₂ NH ₃ ↑, that is, the chemical reaction can be used to dissolve and remove the sacrificial material urea inside the green embryo 11 (not shown in the figure), a hole-like structure is generated inside the green embryo 1 (as shown in FIG. 6). The solubility of urea in water at 20 ° C is 1080g / L. When the green embryo 1 is in water, urea 11 reacts with water to release gas, and then the hydrolyzed green embryo 1 is placed in a heating furnace and heated, and is dried to complete Remove the moisture inside the green body 1. Especially before the drying process, it must be confirmed that most of the urea 11 is dissolved. If it is not completely dissolved, it will cause defects in the drying process, because the urea 11 slowly melts at the melting point of 133 ℃, when the temperature exceeds 152 ℃, the reaction is intensified and the urea 11 is vaporized and decomposed into Ammonia gas and isocyanic acid (HNCO), and continue to decompose when the temperature reaches 160 ℃ -190 ℃ and react with isocyanic acid to form biuret (Biuret). Biuret decomposes and melts at 193 ℃ to promote embryo growth For the porosity of item 1, this stage can be melted more than once according to the requirements of the porosity size or density.

When in the sintering stage d, please refer to figure 7, which is to heat the green body 1 below the melting point temperature of the main component. The mutual movement of atoms in the high temperature changes the distance between the powders, causing a phase change Combining and generating the phenomenon of densification, the principle is to diffuse atoms and crystal growth by converting thermal energy into kinetic energy. The present invention uses solid phase sintering, the sintering time is 2-3 hours, and then use sulfur hexafluoride (SF ₆ ) To protect the gas, because sulfur hexafluoride SF _{6 is} different from other protective gases, it can form a protective film that is not easily oxidized on the surface of the porous magnesium material to achieve a good oxidation prevention effect, and sulfur hexafluoride SF _{6 is} more expensive In addition, in the present invention, the addition amount of sulfur hexafluoride SF _{6 is} 1%, and it is mixed with carbon dioxide (CO ₂ ) as a protective gas in the sintering process.

Regarding the procedure of the sintering stage d, please still read the figure 7 and put the green embryo part 1 that has passed through the drying process into the dry pot 51 and place it in the center of the vacuum furnace 5 before being pumped by the vacuum pump 52 Vacuum to vacuum furnace 5 The pressure in the tube is 3Pa or less (approximately 2 × 10 ^-2 torr), and then filled with a protective gas SF ₆ and CO ₂ mixed gas 53 to prevent the porous green embryo 1 from oxidation and combustion at high temperature reaction. The rising curve of the sintering temperature in the vacuum furnace 5 is 4 ° C per minute, and the sintering temperature is 400 ° C to 600 ° C and the holding time is 2 to 3 hours. The final sintered into a porous magnesium alloy product e will naturally cool in the furnace To room temperature (as shown in Figure 8).

When the present invention is actually used, please refer to Figure 9 and Figure 10 again, the porous magnesium alloy can be made into the required crash material e1 of the automobile industry according to the demand, the fire material e2 required by the construction industry, or The sound-absorbing material e3 of highway engineering, and the porous magnesium material of the present invention can be used as a high-strength, lightweight crash-proof material e1, fire-resistant material e2 and sound-absorbing material e3, which has a wide range of applications and can be used as a variety of industries with its characteristics The required material is indeed an ideal multi-purpose material.

The key of the present invention is to control the parameters of the holding time of powder compaction, the ratio of magnesium powder to aluminum powder, the weight percentage of urea, the time of powder mixing, the temperature of sintering, and the time of sintering. This parameter will affect magnesium The pore size distribution of the alloy and the strength of the magnesium alloy, and the present invention is an ideal porous magnesium material after experiments and tests. Among them, the process technology of the present invention has the following advantages:

1. The present invention uses sulfur hexafluoride (SF ₆ ) + carbon dioxide (CO ₂ ) to prevent magnesium oxidation, and develops a sintering and dissolving process to produce high-performance porous magnesium alloys.

2. The correlation coefficient of hole uniformity and specific compressive strength is 0.4674, that is, the hole uniformity affects the compressive strength, and the present invention can achieve better hole uniformity.

3. According to ANOVA analysis, the control factor affecting the process of porous magnesium material is: urea Proportion, sintering temperature, and holding time are strictly controlled in this process.

4. The porous magnesium alloy of the present invention has more manufacturing temperatures and the porous aluminum material is lower, which is more energy-saving and has the advantage of low cost.

5. The porous magnesium alloy of the present invention has a stronger electromagnetic shielding capability, better bioabsorption performance and biodegradability.

6. The porous magnesium alloy of the present invention has higher strength and rigidity than the porous aluminum material, and is more suitable as a structural material.

In summary, the present invention is developed through testing and improvement, using the best process technology, the developed porous magnesium alloy can be suitable for the automotive industry, construction industry, highway building materials, ships, aviation and aviation, military, Technology ... materials in the field.

Claims (1)

A method of manufacturing a porous magnesium alloy, the main steps are as follows: a, powder material mixing stage; b, green embryo production stage: green embryo production stage: the mixed metal powder is pressed with a hydraulic press In fact, it is pressed uniaxially with a pressure of 200-400Mpa, and is given a pressure of 1 ~ 2 minutes under equal pressure, and then the ejected device is used to eject the formed green embryo in the mold; c. Melting Sacrificial material stage: Melting sacrificial material stage: Put the green embryo into deionized water. The urea inside the green embryo is spherical urea particles. The carbon dioxide and ammonia generated by urea in water can be dissolved and removed. The sacrificial material inside the piece creates a hole-like structure inside the green embryo, and put the hydrolyzed green embryo into a heating furnace to heat it to dry it to remove the moisture inside the green embryo; d. Sintering stage, It is characterized by: in this a, powder material mixing stage: it first sprays 2 vol% ethanol on urea, and then mixes magnesium powder with aluminum powder in a ratio of 9: 1 and urea 40 ~ 60wt.% Together 1 ~ 2 hours to make it evenly mixed D; sintering stage: put the dried green embryo into the center of the vacuum furnace, and then evacuate it with a vacuum pump until the pressure in the tube is less than 3Pa (about 2 × 10 ^-2 torr), and inject protective gas 1% sulfur hexafluoride (SF6) and 99% carbon dioxide (CO ₂ ) mixed gas, and the vacuum furnace sintering temperature rise curve is 4 ℃ per minute, the sintering temperature is 400 ℃ ~ 600 ℃ and holding time 2 After ~ 3 hours, the final sintered porous magnesium alloy is naturally cooled to room temperature in the furnace, and the correlation coefficient between the pore uniformity and specific compressive strength of the porous magnesium alloy is between 0.4 and 0.5.